The present invention relates to an improvement in the brush holder of dynamo-electric machine and, more particularly, to an improvement in a brush holder constructed to permit the replacement of a brush even when the electro-dynamic machine is operating. Still more particularly, the invention is concerned with an improvement of a brush holder having a holder part detachable together with a brush, and provided with a brush retainer for retaining the brush.
In the conventional dynamo-electric machines, the brush holders are fixed to the stationary side of the machine so that the replacement of the brush cannot be made without stopping the dynamo-electric machine. In recent years, there have been proposed various types of brush holders constructed to permit the withdrawal of the brushes even when the dynamo-electric machine is operating. Such brush holders are proposed, for example, in Japanese Patent Laid-open Nos. 125055/1980 and 162859/1980.
In these known arrangements, the whole or a part of the holder is detachable together with the brush held by the holder, and the detachable part of the brush holder is provided with a brush retainer for retaining the brush therein during handling of the brush holder, as well as a spring for pressing the head portion of the brush.
The brush holder constructed as above permits the replacement of the brush without stopping the dynamo-electric machine and, hence, is quite advantageous. However, as a result of a controlled check of conductivity of the brush holders for a long period, the brush holder of the kind described has proved to have the following disadvantage. Namely, in the detachable brush holder of the kind described, there is an appreciable tendency of the brush to jump during long use, as compared with the conventional brush holder that is wholly fixed to the stationary part. This in turn tends to promote sparking on the sliding surface of the collector (slip ring or commutator) to adversely affect the collecting characteristics and causes troubles, such as cracking of the brush.